1. Field of the Invention
The present invention relates to video signal processing devices and displays, and particularly to a video signal processing device that executes signal processing for displaying plural screens (multi-screens) on one display screen and a multi-screen display employing the video signal processing device.
2. Description of the Related Art
In recent years, the size of screens of displays is becoming larger. Furthermore, as the definition of displayed images becomes higher, the amount of information that can be displayed is getting larger. As one of displays having a particularly large screen, a so-called multi-screen (multi-window) display for displaying plural screens (multi-screens) on one display screen is known (refer to e.g. Japanese Patent Laid-open No. 2001-100718).
FIG. 1 shows the basic configuration of a video signal processing device for realizing four multi-screens according to a related art. The video signal processing device includes four video input circuits 101A, 101B, 101C, and 101D and four frame memories 102A, 102B, 102C, and 102D that are provided corresponding to four screens, and a mixer (MIX) 103. For simplification of the drawing, a control system that controls the timings of writing/reading to/from the frame memories 102A, 102B, 102C, and 102D is not shown in the drawing.
The video input circuits 101A, 101B, 101C, and 101D convert a signal of any of various video formats, such as an analog video signal or digital video signal (digital visual interface (DVI) signal, serial digital interface (SDI) signal, high definition (HD)-SDI signal, or the like) into a signal of a common format for use inside the device, such as an R (red) G (green) B (blue) signal.
The frame memories 102A, 102B, 102C, and 102D are used to convert an interlace signal into a progressive signal (I/P conversion) and change the size of input video (scaling). In addition, the frame memories 102A, 102B, 102C, and 102D output video signals VIDEO11, VIDEO12, VIDEO13, and VIDEO14 in accordance with a reference synchronizing signal for superposition of the video signals with each other. The video signals VIDEO11, VIDEO12, VIDEO13, and VIDEO14 are output after being reduced to e.g. about ¼.
The mixer 103 superimposes (mixes) the video signals VIDEO11, VIDEO12, VIDEO13, and VIDEO14 output from the frame memories 102A, 102B, 102C, and 102D, and outputs the resultant signal as one video signal VIDEO100.
FIG. 2 shows an image of the mixing of four video signals VIDEO11, VIDEO12, VIDEO13, and VIDEO14 into one video signal VIDEO100 and the displaying of the video signal VIDEO100.
As is apparent from FIG. 2, the video signal processing device having the above-described configuration allows the video signals VIDEO11, VIDEO12, VIDEO13, and VIDEO14 input through multi-channels (four channels, in the present example) to be displayed on one display screen.
However, in the video signal processing device with the above-described configuration according to a related art, the video input circuits 101A, 101B, 101C, and 101D are disposed in parallel for video inputs on plural channels. This configuration imposes a limitation on the number of inputs in the system and therefore is insufficient in versatility. For example, when a system configuration with four inputs like the configuration of FIG. 1 is employed, it is impossible to input video signals through five or more inputs.
On the other hand, when a system configuration with eight inputs is employed, for a user who uses only four inputs, the circuit part corresponding to the remaining four inputs is unnecessary. Accordingly, this system is unnecessarily expensive for this user. It would be also possible to employ a configuration from which the video input circuits and the frame memories corresponding to the remaining four inputs have been eliminated in advance. However, even in this configuration, at least the mixer 103 needs to have a configuration compatible with the maximum eight inputs. Therefore, for the user who uses only four inputs, at least the circuit part of the mixer 103 corresponding to the remaining four inputs is unnecessary.